In a typical double row antifriction bearing, such as a roller bearing as shown in FIG. 5, there is provided a housing in which an inner race means and an outer race means are mounted. Usually, one of said race means, such as the outer race means, consists of two spaced apart race members (each with a raceway to receive the bearing rollers) while the other race means (the inner race means) may be a single race member with two raceways to receive the bearing rollers. Usually, one of the race members of the split race means abuts against one end of the housing, while the other race member of the split race means abuts against a nut received in the housing. Although the bearing shown in FIG. 5 is a spherical bearing, a similar arrangement can be used with other multi-row bearings such as tapered roller or ball bearings.
When the nut is tightened in the housing a preload force is placed on the bearing members to prevent any looseness or play in the assembly under fluctuating loads.
Assuming the outer race means consists of two race members and the inner race means consists of a single race member in a double row spherical roller bearing, the preload force will be transmitted from the nut to one outer race member, through one row of rollers to the inner race member. From the inner race member, the force will be transmitted through the other row of rollers to the other outer race member, and back to the housing. One difficulty with this arrangement is that any wear of the bearing elements, or looseness of the nut, diminishes the preload force until vibration of the bearing members will begin. Another difficulty with this arrangement is that the preload is added to the fluctuating load on the bearing, to increase the wear on the rollers and race members.